"The San Francisco 49ers announced on Monday that QB Jimmy Garoppolo underwent an MRI this morning and it has been determined that he has suffered a torn left ACL," the statement read.

No timescale has been put on his recovery as yet, but head coach Kyle Shanahan is to address the media later on Monday.

Garoppolo completed 20 of 30 passes for 251 yards and two touchdowns in the 38-27 loss.

The Niners are expected to make C.J. Beathard the team's starter in Garoppolo's absence. He previously lost the job about a month after Garoppolo was acquired in a trade last year from the New England Patriots.